Copper-Catalyzed Aerobic CC Bond Cleavage of Lactols with N-Hydroxy Phthalimide for Synthesis of Lactones
作者:Ya Lin Tnay、Shunsuke Chiba
DOI:10.1002/asia.201403196
日期:2015.4
The transformation of cyclichemiacetals (lactols) into lactones has been achieved by Cu‐catalyzed aerobic CC bond cleavage in the presence of N‐hydroxy phthalimide (NHPI). The present process is composed of a multistep sequence including a) formation of exo‐cyclic enol ethers by dehydration; b) addition of phthalimide N‐oxyl radical to the enol ethers followed by trapping of the resulting C‐radicals
The reactions of diazo compounds with lactones. Part 1. Cyclopropanespiro-β-lactones from diketene: synthesis and reactions
作者:Paul V. Murphy、Timothy J. O’Sullivan、Niall W. A. Geraghty
DOI:10.1039/b001393p
日期:——
The cyclopropanespiro-β-lactones 3, 4 and 12 can be prepared by the metal catalysed, or photochemically promoted decomposition reactions of diazocompounds in the presence of diketene. The thermal reactions of these compounds give a variety of products depending on the nature of the spirolactone; these include a furan 9a, 1,4-dicarbonyl compounds 18aâc and 19b, a pyranone 20b, furanones 21a, 21f and 22a and the enol 16. The boron trifluoride promoted reaction of a mixture of 3b and 4b gives a β-ketoacid. Mechanisms are proposed for the formation of these products. The rearrangment of the cyclopropanespiro-β-lactones to furan-2(5H)-ones and furan-2-(3H)-ones 6â8, 21a, 21f, 22a and 24 is shown to be a general reaction that involves metal catalysis. A mechanism based on formation of a metallocycle by a novel insertion of the metal into the CâO bond of the β-lactone ring is proposed for this rearrangement. This accounts for the observed features of the reaction.